1. Field of the Invention
The present invention is directed to a power plant with a coal gasification device, a gas generator and a reheater. A process for operating the power plant of the invention, and the use of individual components thereof is also disclosed.
2. Description of the Related Art
The environmental and economic requirements on power plants such as are described, for example, in DE 101 55 508 C5 and DE 198 29 088 C2 (U.S. Pat. No. 6,256,978), increase continually. Particularly for the reduction of carbon dioxide, there are two theoretical concepts: one is to increase cycle efficiency, and the other is to capture carbon dioxide (CO2) from the power plant process and reuse it.
With the tested and affordable elements at hand, only CO2 capture is currently feasible. The IGCC process, on the one hand, is known for this purpose, wherein the pollutants specific to carbon that are contained in the raw gas such as H2S, COS, NH3, HCN and the like are already removed before it is combusted in a gas turbine in a special purification process. Carbon monoxide contained in the raw gas is converted to hydrogen and CO2 by another process step, the CO shift, and is separated out prior to combustion. These separating processes require a high expenditure on apparatus.
In addition to the IGCC process, the oxy-fuel process is also known, for example, from DE 10 2005 026 534 A1 (WO2006/131283), in which the combustion is carried out with pure oxygen and the CO2 is separated in a flue gas condenser.
The integrated gasification simple cycle (IGSC) process known, for example, from the articles “Lose the carbon, not your capacity”, tce today, December 2008/January 2009, pages 43-44, and “Competition hots up in the UK . . . ”, Modern Power Systems, May 2008, page 30, combines the advantages of the IGCC and oxy-fuel processes.
However, because it causes an increase in the acid dew point, the high partial pressure of SO2 and water vapor at high gas pressure requires a constant feedwater temperature at the entrance into the boiler independent from load. This substantially limits flexibility in the operation of the power plant. Since the feedwater temperature drops below the acid dew point as the load decreases, the power plant must still be operated constantly at the full load point.
Therefore, it is an object of the present invention to improve the known power plant process.